1. Field of the Invention
The present invention relates to an extendible whip antenna assembly for a mobile terminal used in mobile communication.
2. Description of the Related Art
In mobile communication, a mobile terminal or a mobile radio apparatus must constantly exchange information with base stations both in a stand-by state and during communication.
As antennas therefor, a small antenna such as a helical antenna is used in the stand-by state while a whip antenna to used during communication. These antennas are combined together to form an extendible whip antenna assembly which can be retracted into a housing of the mobile radio apparatus.
The extendible whip antenna assembly has a helical antenna which is fixed to the housing of the mobile radio apparatus via a holder serving as a feeding point, and a whip antenna which passes through the helical antenna and is slidable in the longitudinal direction.
A stopper of an electric conductor is mounted on one and of the whip antenna within the housing, and a dummy antenna portion is attached to the other end of the whip antenna. The holder is made of an electric conductor and has a flexible contact member of an electric conductor.
When extended, the stopper of the whip antenna to fitted into the flexible contact member and makes contact therewith, and the feeding point is commonly connected to the helical antenna and the whip antenna.
On the other hand, when the extendible whip antenna assembly is retracted into the housing, the dummy antenna portion is fitted into the flexible contact member and makes contact therewith so that the feeding point is connected to the helical antenna alone.
For selectively maintaining the extended position and the retracted position, the conventional extendible whip antenna assembly has at least three parts, i.e., a stopper at the lower end of the whip antenna, a holder connected to the helical antenna, and a flexible contact member.
The flexible contact member is in the holder connected to the helical antenna and, therefore, has a problem that it is difficult to adjust a friction with the whip antenna extended into the extended position.
Also, in order to place the flexible contact member within the holder, the whip element of the whip antenna must have a diameter sufficiently small as compared with a diameter of a screw for attaching the holder to the housing. In the event that the diameter of the whip element is not sufficiently small, the flexible contact member cannot be placed within the holder.
Accordingly, it is an object of the present invention to provide an extendible whip antenna assembly, wherein the whip antenna can be maintained in the extended position without using a flexible contact member within the holder connected to the helical antenna, and wherein a feeding point can be commonly connected to the whip antenna and the helical antenna, thereby reducing the number of parts for selectively maintaining the extended position and the retracted position, to thereby realize reduction in cost and weight.
It is another object of the present invention to provide an extendible whip antenna assembly, wherein it is easy to adjust the friction force applied to the whip antenna when it is extended to the extended position.
It is yet another object of the present invention to provide an extendible whip antenna assembly, wherein the whip antenna can be connected to the feeding point in parallel with the helical antenna even in the event that the diameter of the whip antenna element is not sufficiently smaller than the diameter of the screw for attaching the holder to the housing.
According to the present invention, there is provided an extendible whip antenna assembly comprising a helical antenna mounted on an outside surface of a housing of a radio communication equipment, a whip antenna slidably mounted on the housing to be movable between a retracted position where the whip antenna is retracted in the housing and an extended position where the whip antenna is projected from the helical antenna toward the outside of the housing, and feeding means for stopping the whip antenna in the extended position and for commonly feeding the whip antenna and the helical antenna. The feeding means comprises a stopper of an elastic electric conductive material and mounted on one end of the whip antenna for securing the whip antenna to the housing in an extended position, and a holder of an electric conductive material electrically connected to a transceiver circuit within the housing and fixing the helical antenna to the housing. The holder is connected to the stopper when the whip antenna is in the extended position.